Broadly, a “smartcard” (or “smart card”), chip card, or integrated circuit card (ICC) is any pocket-sized card that has embedded integrated circuits. Smartcards are usually made of layers of plastic, generally polyvinyl chloride, but sometimes polyethylene terephthalate based polyesters, acrylonitrile butadiene styrene or polycarbonate. Smartcards can be either contact or contactless smartcard. Some “dual interface” smartcards may incorporate contact and contactless functionality. Modern contactless cards generally also have contact capability.
A smartcard is an example of an RFID device that has a transponder chip module (TCM) or an antenna module (AM) disposed in a card body (CB) or inlay substrate.
The antenna module (AM) or antenna chip module, which may be referred to as a transponder chip module (TCM) may generally comprise:                a module tape (MT) or chip carrier tape (CCT), more generally, simply a support “substrate”;        an RFID chip (CM, IC) which may be a bare, unpackaged silicon die or a chip module (a die with leadframe, interposer, carrier or the like), typically disposed on a “face-down side” or “bond side” or “chip side” (or surface) of the module tape (MT);        the RFID chip may have an antenna integrated therein, but generally a separate module antenna (MA) is typically provided to effect contactless communication between the RFID chip and another RFID device such as an external contactless reader; and        a module antenna (MA) or antenna structure (AS), typically disposed on the same face-down side of the module tape (MT) as the RFID chip (IC), and connected therewith, for implementing a contactless interface, such as ISO 14443 and NFC/ISO 15693 with a contactless reader or other RFID device.        a wire wound antenna may be mounted to the module tape        a silicon capacitor may be placed and connected to the module tape        
The module antenna (MA) may be a planar antenna (PA) which is etched from a foil (which may be supported by the module tape MT) to have a spiral track having a number of turns. The track (hence turns) may measure approximately 100 μm in width. Spaces between adjacent turns of the spiral track may measure approximately 25 μm in width. Etching may be performed by chemical means, or laser ablation, or a combination thereof.
When operating in a contactless mode, a passive antenna module (AM) or transponder chip module (TCM) may be powered by RF from an external RFID reader, and may also communicate by RF with the external RFID reader.
A dual-interface antenna module (AM) or transponder chip module (TCM) may also have a contact pad array (CPA), typically comprising 6 or 8 contact pads (CP, or “ISO pads”) disposed on a “face-up side” or “contact side” (or surface) of the module tape (MT), for interfacing with a contact reader in a contact mode (ISO 7816). A connection bridge (CBR) may be disposed on the face-up side of the tape for effecting a connection between two components such as the module antenna and the RFID chip on the other face-down side of the module tape.
Two connection bridges (CBR) on the face up side (contact pads) of a module tape may permit the interconnection of additional components or to modify the electrical parameters of the planar antenna on the rear side of the module tape by introducing clock-wise and anti-clockwise, or interleaving antenna tracks. Connection bridges for dual-interface transponder chip modules may be described in US 20150129665, 14 May 2014.
A smart card is typically “credit card” size having dimensions for identification cards as defined by ISO/IEC 7810, wherein the ID-1 format specifies a size of 85.60×53.98 mm, with rounded corners. A smartcard may include a card body (CB) plus front and rear printed layers and clear overlay layers, and may have an overall thickness of 0.76 mm (760 μm).
A conventional antenna module (AM) or transponder chip module (TCM) may be generally rectangular, having four sides, and measuring approximately 8.2 mm×10.8 mm for a 6-contact module and 11.8 mm×13.0 mm for an 8-contact module. As disclosed herein, a generally rectangular transponder chip module (TCM) may have a larger or smaller form factor than a conventional transponder chip module (TCM). Alternatively, the transponder chip module (TCM) may be round, elliptical, or other non-rectangular shape.
A module antenna (MA) may be disposed on the module tape (MT) for implementing a contactless interface, such as ISO 14443 and NFC/ISO 15693. Contact pads (CP) may be disposed on the module tape (MT) for implementing a contact interface, such as ISO 7816. The module antenna (MA) may be wire-wound, or etched, for example:                The module antenna (MA) may comprise several turns of wire, such as 50 μm diameter insulated wire. Reference may be made to U.S. Pat. No. 6,378,774 (2002, Toppan), for example FIGS. 12A, B thereof.        The module antenna (MA) may be a chemically-etched planar antenna (PA) structure. Reference may be made to U.S. Pat. No. 8,100,337 (2012, SPS), for example FIG. 3 thereof.        The module antenna (MA) may comprise a laser-etched planar antenna (PA) structure (LES). Reference may be made to US 20140284386 (U.S. Pat. No. 9,272,370).        
A planar antenna (PA) structure, or simply “planar antenna (PA)”, whether chemically-etched (CES) or laser-etched (LES), is a type of antenna structure (AS) and may comprise a long conductive trace or track having two ends, in the form of a planar, rectangular spiral, disposed in an outer area of a module tape (MT), surrounding the RFID chip on the face-down side of the module tape. This will result in a number of traces or tracks (actually, one long spiraling trace or track), separated by spaces (actually, one long spiraling space). The track (or trace) width may be approximately 100 μm. The planar antenna may be fabricated on other than the module tape, such as on a separate substrate, and joined to the module tape. An example of a laser-etched module antenna (MA) which is a planar antenna (PA) may be found in U.S. Pat. No. 9,272,370 (2016 Mar. 1; Finn et al.). The terms module antenna and planar antenna may be used interchangeably herein, unless otherwise specified.
Substituting Booster Antennas (BAs) with Coupling Frames (CFs)
Passive near-field RFID systems for dual interface payment smartcards, operating at 13.56 MHz (HF) as defined by the ISO/IEC 14443 standard for proximity/contactless integrated circuit cards, generally require a booster antenna for inductive coupling with a contactless reader, and to enhance the read/write performance of a transponder chip module. Reference may be made to U.S. Pat. No. 6,378,774 (2002, Toppan).
A coupling frame (CF) made of a metal foil layer having an optimized and well-controlled slit (S) extending through the metal layer, and strategically located vis-à-vis the transponder chip module (TCM), and may be a substitute for (replace, obviate the need for) a large area receiver coil (booster antenna) in a smartcard body which couples with the transponder chip module (TCM). The slit in the coupling frame may be referred to as a “slot”. A non-conductive strip (or stripe. NCS) which extends through the metal foil may be used in lieu of a slit, providing a similar discontinuity in the metal foil for concentrating eddy currents and facilitating interaction with the module antenna (MA).
A module antenna (MA) connected to an RFID chip (CM), typically on a substrate or module tape (MT), may be referred to as a “transponder chip module”, or simply as a “transponder”, or as a “module”.
The transponder chip module (TCM) may have a chemical (CES) or laser-etched (LES) antenna structure. The slit (S) or nonconductive stripe (NCS) in the coupling frame (CF), a patterned metal foil layer in conjunction with a rectangular module opening/cut-out, overlaps at least a portion of the module antenna (MA) of the transponder chip module (TCM).
When a dual interface smartcard is subject to an external RF field generated by a contactless terminal, the main role of the coupling frame (CF) may be to act as a matching transformer coupling the magnetic flux penetrating its relatively large card body area (˜46 cm2) to the module antenna (MA) of the transponder chip module (TCM) via the slit (S). The resulting eddy (Foucault) current distribution may be at maximum at the free edges of the coupling frame (CF). The field may be concentrated along the slit (S), with peak field intensity near the top (inner-most section) of the slit (S). In addition, the field may be concentrated to a lesser extent along the coupling frame (CF) perimeter itself.
Reference may be made to US 20150136858 (U.S. Pat. No. 9,390,364), US 20140361086 (U.S. Pat. No. 9,475,086) and US 20150021403 (U.S. Pat. No. 9,798,968), all of which show examples of transponder chip modules (and coupling frames).
In the main, hereinafter, transponder chip modules (TCM) and the RFID devices such as payment objects incorporating the transponder chip modules may be passive devices, not having a battery and harvesting power from an external contactless reader (ISO 14443). However, some of the teachings presented herein may find applicability with cards having self-contained power sources, such as small batteries or supercapacitors.
Transponders can be attached to metal surfaces, if the effects of the metal can be shielded, which is usually achieved using magnetic materials, such as ferrite, and spacing the transponder at a distance off the surface of the metal. See, for example, U.S. Pat. No. 8,366,009. See also US 20090159657 (2009 Jun. 25; Chen et al.) which discloses a contactless integrated circuit card system. A shielding member could be a conductor in form of a sheet, plate, or foil, and could also be a soft magnetic member.
Consideration may also be given to an edge-to-edge metal layer in the stack-up construction of a metal embedded card (Plastic-Metal-Plastic), whereby the metal layer has a discontinuity in its conductive surface and an opening to accept a booster antenna which inductively couples with a transponder chip module. In combination with one another, the metal layer and booster antenna may capture the electromagnetic field. The booster antenna may be adjacent or overlapping the metal layer.